Bastien Dalla Piazza

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Magnetism has been predicted to occur in systems in which dipolar interactions dominate exchange. We present neutron scattering, specific heat, and magnetic susceptibility data for LiErF4, establishing it as a model dipolar-coupled antiferromagnet with pla ...

The first part of this thesis presents the theoretical study of an anomaly of unknown origin in the excitation spectrum of the Quantumspin-1/2 Heisenberg Square lattice Anti-Ferromagnet. The anomaly manifests itself in Inelastic Neutron Scattering data for ...

We investigate the spin-1/2 Heisenberg model on a rectangular lattice, using the Gutzwiller projected variational wave function known as the staggered flux state. Using Monte Carlo techniques, the variational parameters and instantaneous spin-spin correlat ...

We present a systematic study of the crystal-field interactions in the LiRF4 (R = Gd, Ho, Er, Tm, and Yb) family of rare-earth magnets. Using detailed inelastic neutron scattering measurements, we have been able to quantify the transition energies and wave ...

We present the experimental phase diagram of LiHoxEr1-xF4, a dilution series of dipolar-coupled model magnets. The phase diagram was determined using a combination of ac susceptibility and neutron scattering. Three unique phases in addition to the Ising fe ...

Using low-energy projection of the one-band t-t′-t′′ Hubbard model we derive an effective spin Hamiltonian and its spin-wave expansion to order 1/S. We fit the spin-wave dispersion of several parent compounds to the high-temperature superconducting cuprate ...

Quantum magnets have occupied the fertile ground between many-body theory and low-temperature experiments on real materials since the early days of quantum mechanics. However, our understanding of even deceptively simple systems of interacting spin-1/2 par ...

We investigate by resonant inelastic x-ray scattering the magnetic excitations in thin films of tetragonal CuO. We identify a spin wave excitation, dispersing on two cupratelike antiferromagnetic sublattices. Its energy at the boundary of the Brillouin zon ...

The novel iridate Ba8Al2IrO14 was prepared as single crystals by self-flux method, thereby providing a rare example of an all-Ir(VI) compound that can be synthesized under ambient pressure conditions. The preparation of all-Ir6+ iridate without using tradi ...

We measured the momentum dependence of magnetic excitations in the model spin-1/2 2D antiferromagnetic insulator Sr2CuO2Cl2 (SCOC). We identify a single-spin-wave feature and a multimagnon continuum, with different polarization dependences. The spin waves ...

We present a study of the model spin-glass LiHo0.5Er0.5F4 using simultaneous ac susceptibility, magnetization, and magnetocaloric effect measurements along with small angle neutron scattering ( SANS) at sub-Kelvin temperatures. All measured bulk quantities ...

We study the zero-point and thermal ionic motion in La2CuO4 by means of high-resolution neutron-diffraction experiments. Our results demonstrate anisotropic motion of O and, to a lesser extent, Cu ions, both consistent with the structure of coupled CuO6 oc ...

The high-T-c cuprate superconductors are close to antiferromagnetic order. Recent measurements of magnetic excitations have reported an intriguing similarity to the spin wavesmagnons- of the antiferromagnetic insulating parent compounds, suggesting that ma ...

Bastien Dalla Piazza

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Dipolar Antiferromagnetism and Quantum Criticality in LiErF4

Theories of Experimentally Observed Excitation Spectra of Square Lattice Antiferromagnets

Staggered flux state for rectangular-lattice spin-1/2 Heisenberg antiferromagnets

Neutron spectroscopic study of crystal-field excitations and the effect of the crystal field on dipolar magnetism in LiRF4 (R = Gd, Ho, Er, Tm, and Yb)

Phase diagram with an enhanced spin-glass region of the mixed Ising–XY magnet LiHoxEr1-xF4

Unified one-band Hubbard model for magnetic and electronic spectra of the parent compounds of cuprate superconductors

Fractional excitations in the square-lattice quantum antiferromagnet

Magnons in tetragonal CuO

Crystal Structure, Transport, and Magnetic Properties of an Ir6+ Compound Ba8Al2IrO14

Measurement of Magnetic Excitations in the Two-Dimensional Antiferromagnetic Sr2CuO2Cl2 Insulator Using Resonant X-Ray Scattering: Evidence for Extended Interactions

Nonequilibrium hysteresis and spin relaxation in the mixed-anisotropy dipolar-coupled spin-glass LiHo0.5Er0.5F4

Quantum and thermal ionic motion, oxygen isotope effect, and superexchange distribution in La2CuO4

Anisotropic softening of magnetic excitations along the nodal direction in superconducting cuprates